In Part One, chapter 4, Winston Smith is given the task of rewriting an entire article of the Times because it references a person that supposedly never existed. In Oceania, citizens who offend or threaten the Party simply disappear and are "vaporized." Winston's job in the Ministry of Truth is to continually alter articles and other pieces of historically significant literature in order to corroborate with the Party's current political agenda. One of the chief features of Big Brother's rule is the mutability of the past and the government's ability to alter history via continuous revisions and utilizing "doublethink." When political dissidents are "vaporized," their names and identities are completely erased from historical records. The Party refers to a person who has seemingly never existed as an "UNPERSON."
Since the article Winston alters in chapter 4 refers to an "UNPERSON" named Comrade Withers, he simply fabricates another honorable soldier named Comrade Ogilvy to commemorate in the article. Essentially, Winston alters history by creating another person, who loyally and courageously served the Party, while simultaneously erasing another person's personal life and accomplishments from history. This is just one example of how the Party controls the past by continually altering and revising literature to corroborate their current political agenda.